Components and catalysts for the polymerization of olefins

ABSTRACT

Catalysts for the polymerization of alpha-olefins, which comprise the product of the reaction between: 
     (a) a metallorganic compound of Al; 
     (b) an electron-donor compound reactive towards MgCl 2  but which is not completely complexed with AlEt 3 , at the equivalent point of a potentiometric titration under standard conditions; 
     (c) a solid comprising a halogenated Ti compound and an electron-donor belonging to particular classes of compounds and being extractable with AlEt 3  for at least 70% by mols from the solid, the surface area of which after extraction is higher than 20 m 2  /g. 
     The present invention refers to new supported components of catalysts for the polymerization of olefins CH 2  ═CHR, in which R is an alkyl with 1-4 carbon atoms or an aryl, and of mixtures of such olefins with each other and/or with ethylene, and to the catalysts obtained from such components.

This application is a continuation of application Ser. No. 013,148,filed Feb. 10, 1987, which in turn is a Continuation of application Ser.No. 855,374, filed Apr. 24, 1986, which in turn is a continuation ofapplication Ser. No. 729,124, filed May 1, 1985, all three nowabandoned, which in turn is a Continuation of application Ser. No.465,594, filed Feb. 10, 1983 now U.S. Pat. No. 4,522,930.

BACKGROUND OF THE INVENTION

Catalysts endowed with high activity and high stereospecificity,obtained from metalorganic Al compounds, silicon compounds containingSi--O--C, Si--OCOR or Si--NR₂ bonds and from a solid comprising ahalogenated titanium compound and an electron-donor compound, bothsupported on an active Mg halide have been disclosed, the electron-donorcompound being selected from specific classes of ester.

THE PRESENT INVENTION

We have now found, unexpectedly, that it is possible to prepare highlyactive and highly stereospecific catalysts also by employingelectron-donor compounds different from those described in the earlierpatent applications, provided that the employed electron-donor compoundbelonds to certain classes of compounds, as specified hereinafter, andis for at least 70% by mols extractable from the solid catalystcomponent by reaction under standard conditions with Al-triethyl, andthat the surface area of the product after extraction is not less than20 m² /g.

The catalysts of the invention comprise the product of the reactionbetween at least the following components:

(a) an Al-alkyl compound, preferably an Al-trialkyl or a compoundcontaining two or more Al atoms linked to each other through oxygen ornitrogen atoms or through SO₄ or SO₃ groups;

(b) an electron-donor compound (or Lewis base) which, under the standardconditions of measurement as indicated hereinafter, is reactive towardsMgCl₂ but which results not to be completely complexed with AlEt₃ at theequivalent point of a potentiometric titration under standardconditions;

(c) a solid comprising a Ti halide and an electron-donor compound bothsupported on a Mg halide, such an electron-donor compound being selectedfrom the classes of: ethers, ketones, lactones, electron-donor compoundscontaining N, P and/or S atoms, and from the following esters:

(1) hydrocarbyl esters of linear saturated dicarboxylic acids containingfrom 2 to 5 C atoms;

(2) esters of unsaturated polycarboxylic acids, in which two carboxylgroups are linked to vicinal, double bond-forming carbon atoms and inwhich the hydrocarbyl radical or radicals of the COOR groups are linearsaturated or unsaturated radicals or cycloaliphatic radicals with 1-20 Catoms or hydrocarbyl esters of unsaturated linear or branchedpolycarboxylic acids with 1-20 carbon atoms, in which the carboxy groupsare not linked to vicinal double bond-forming carbon atoms;

(3) hydrocarbyl esters of aromatic meta- and paradicarboxylic acids andhydrocarbyl esters of aromatic polycarboxylic acids containing more thantwo carboxyl groups;

(4) hydrocarbyl esters of aromatic hydroxy compounds containing the OHgroups in meta- or para-position, and esters of aromatic hydroxy acidsthe OH groups of which are in meta- or para-position with respect to thecarboxyl group;

(5) esters RCOOR' the hydrocarbyl groups R and R' of which can be thesame or different, and which are linear saturated or unsaturatedradicals or cycloaliphatic radicals having from 1 to 20 carbon atoms, orR is an aryl, alkylaryl or cycloalkyl with 5-20 carbon atoms and R' is ahydrocarbyl radical or a heterocyclic ring with 5-7 atoms in the ring;

(6) hydrocarbyl esters of polycarboxylic acids in which at least onecarboxyl group is linked to an aromatic ring and at least one other islinked to a carbon atom of an aliphatic group or to a cycloaliphaticring or at least two carboxyl groups are linked to an aromatic ringthrough an alkylene group;

(7) esters of aromatic polycarboxylic acids containing at least twonon-condensed aromatic rings, each bearing a carboxyl group;

(8) esters of carbonic acid with glycols and carbonic acid derivativesof formula RO--CO--OR' wherein R and R' are the same or different acylgroups with 1-20 carbon atoms;

(9) esters of polyols and monohydroxy-phenols; and

(10) hydrocarbyl esters of acetylenic acids; the electron-donor compoundbeing extractable from the solid for at least 70% by mols withAl-triethyl under standard measurement conditions, and the surface areaof the solid subjected to extraction being higher than 20 m² /g.

Examples of electron-donor compounds belonging to the above specifiedclasses and suitable for the preparation of the catalyst components ofthe invention are: diisoamyl ether, diisobutyl ether, benzophenone,triphenyl phosphite, phenyl propionate, di-n-butyl succinate, diisobutylsuccinate, di-n-butyl malonate, diethyl allylmalonate, di-n-butylmaleate, ethyl and propyl trichloroacetate, POCl₃, triphenylphosphine,α-methyl-α-phenyl-butyrolactone, 1,6-hexandiol di-p-toluate,1,4-butandiol di-p-toluate, ethyl benzoyl carbonate (C₆ H₅CO--O--CO--OC₂ H₅), diisobutyl ester of ophenylene diacetic acid.

It is understood that the above classes of esters include also thederivatives thereof as, for instance, the derivatives containing halogenatoms or unsaturated hydrocarbyl radicals. Ethyl trichloroacetate anddiethylallyl malonate listed above are examples of such derivatives.

All the above compounds are extractable from the solid catalystcomponent for at least 70% by mols by reaction with Al-triethyl. Thesurface area of the solid after the treatment with Al-triethyl is higherthan 20 m² /g and in the case of very active catalysts higher than 100m² /g and in general comprised between 100 and 300 m² /g.

In the case of weak electron-donors, as certain ethers, it has beenfound that the ether can be substantially removed from the catalyticsolid during the preparation if the latter comprises treatments withexcess TiCl₄ and/or washings with halogenated solvents. Nevertheless,also these catalyst components fall within the scope of the presentinvention. It is understood that the above donor compounds, whensubjected to the extractability test with Al-triethyl before the abovementioned treatments, comply with the test.

It has also been found that it is possible to obtain catalyst componentsaccording to the invention also by employing certain electron-donorcompounds, such as alkyl, cycloalkyl or aryl esters of aromaticmonocarboxylic acids, which in the preparation conditions hitherto knowndo not from catalyst components satisfying the requirements of thisinvention.

The components according to the invention are prepared by methods whichconsist in hot washing with a halogenated hydrocarbon solvent aco-ground mixture comprising the ester, the Ti compound and the Mghalide.

By Ti halides and electron-donor compounds supported on a Mg dihalideare meant the compounds non-extractable from component (c) aftertreatment with boiling 1,2-dichloroethane for 2 hours (concentration ofthe solid in the suspension: 5% by weight).

The compounds reactive towards MgCl₂ are those which under the standardconditions of the reaction remain fixed on the Mg halide for at least20% by mols.

Components (a), (b) and (c) are reacted with each other in any order;nevertheless, components (a) and (b) are preferably pre-mixed beforebeing contacted with component (c).

Components (c) can be pre-mixed with component (a) and/or with component(b). The pre-mixing of (a) and (b) is carried out at temperaturesusually comprised between room temperature and the temperature employedin the polymerization.

The pre-reaction of (c) and (b) can be carried out also at highertemperatures. Compound (b) can also be incorporated in and reacted withcomponent (c) itself.

Component (b) is reacted in a molar ratio with respect to thehalogenated Ti compound supported on component (c) of at least 1, and ina molar ratio with respect to the Al-alkyl compound employed ascomponent (a) lower than 20 and preferably comprised between 0.05 and 1.Ratios higher than 1 can be employed with compounds (b) not complexingor only weakly complexing Al-triethyl also under conditions promotingsuch complex formation.

In component (c) the molar ratio between the Mg dihalide and thehalogenated Ti compound supported on it is comprised between 1 and 500,and the molar ratio between the halogenated Ti compound and theelectron-donor both supported on the Mg dihalide is comprised between0.1 and 50.

The electron-donor compounds as defined in (b) does not show at theequivalent point of the titration test with Al-triethyl (carried outunder the standard conditions indicated hereinafter) any logarithmicvariation of potential i.e., a wave, in the titration curve.

A completely different situation occurs in the case of amines likeisoquinoline or esters like ethyl-p-toluate or ethylbenzoate, whereinthe titration curve shows a wave at the equivalent point. The absence ofa wave at the equivalent point indicates that electron-donor compound(b) is present, at least in part, in non-complexed form withAl-triethyl.

Electron-donor compounds containing active hydrogen atoms reactivetowards Al-triethyl, i.e., capable of substitution reactions withAl-triethyl, are prereacted with Al-triethyl before subjecting the sameto the complexion test. In the titration test the equivalent point isgenerally referred to the use of 1 mol of Al-triethyl per mol of donor.

Compounds (b) can be used in mixture, in a wide range, with donorsforming complexes with Al-triethyl when titrated according to the testset forth above.

The titration of the mixtures containing significant amounts of thecomplexing donors, shows the potential variation due to the presence ofsaid complexing donors.

However, the polymerization performance of the catalysts obtained byusing the above mixtures as component (b) is not significantly reducedby the presence of the complexing donor.

The compound (b) is selected in particular from compounds of generalformula:

    RmSiYnXp

wherein:

R is an alkyl, alkenyl, aryl, arylalkyl or cycloalkyl radical with 1-20carbon atoms;

Y is a --OR', --OCOR' or --NR'₂ radical in which R', the same as ordifferent from R, has the same meaning as R;

X is a halogen or hydrogen atom or a --OCOR" or --NR"₂ group in whichR", the same as or different from R', has the same meaning as R'; m, n,p are numbers comprised:

m from 0 to 3, n from 1 to 4 and p from 0 to 1; m+n+p is equal to 4.

Preferred silicon compounds are: phenyl alkoxy silanes such as phenyltriethoxy or phenyl trimethoxy silane, diphenyl dimethoxy and diphenyldiethoxysilane, monochlorophenyl diethoxy silane; alkyl alkoxy silanessuch as ethyl triethoxy silane, ethyl triisopropoxy silane.

In the catalysts according to the invention, the silicon compound ispresent in combined form in the solid product of the reaction betweenthe various components forming the catalyst in a molar ratio between thesilicon compound and the halogenated Ti compound higher than 0.05 and ingeneral comprised between 0.1 and 5.

Other suitable compounds (b) are: 2,2,6,6-tetramethylpiperidine,2,2,5,5-tetramethylpyrrolidine,2,2,6,6-tetramethylpiperidide-Al-diethyl, Al-dichloro-monophenoxy.

The Al-alkyl compounds of component (a) include the Al-trialkyls, suchas for instance AlEt₃, Al(i-C₃ H₇)₃, AlEt₂ H, and compounds containingtwo or more Al atoms linked to each other through hetero-atoms, such as:(C₂ H₅)₂ Al--O--Al(C₂ H₅)₂, (C₂ H₅)₂ Al--N--Al(C₂ H₅)₂, ##STR1##

As indicated, Al-alkyl compounds in which Al atoms are linked throughgroups like SO₄ or SO₃ are also suitable.

The Al-alkyl compounds can be employed in admixture with Al-alkylhalides, as AlEt₂ Cl.

Component (c) is prepared according to various methods. One of theseconsists in co-grinding the Mg halide and the electron-donor compounduntil the product, after extraction with Al-triethyl under standardconditions, shows a surface area higher than 20 m² /g, and in reactingsubsequently the ground product with the Ti compound.

Preparations of this type are described in British Patent No. 1,559,194.

Another method consists in reacting adduct Mg halide/alcohol with a Ticompound in the presence of the electron-donor compound. This method isdescribed in Belgian Patent No. 868,682.

According to another method, described in published German patentapplication No. 3,022,738, the adduct Mg dihalide/alcohol is reacted inliquid form with the halogenated Ti compound and with the electron-donorcompound.

Other methods are described in published German patent application No.2,924,029, U.S. Pat. No. 4,220,554 and Italian patent application No.27261/79.

Another method consists in co-grinding the Mg dihalide, the halogenatedTi compound and the electron-donor compound until the Mg dihalide isactivated, in treating a suspension of the ground product in ahalogenated hydrocarbon, as 1,2-dichloroethane, chlorobenzene, methylenedichloride, or hexachloroethane, and in separating the solid from theliquid halogenated hydrogenated. This method is particularly suitablefor preparing catalyst components satisfying the extractabilitycriterion of the present invention when esters of aromaticmonocarboxylic acids, such as, for instance, alkyl esters of benzoicacid, are used as electron-donor compounds.

The treatment is carried out at temperatures comprised between 40° C.and the boiling point of the halogenated hydrocarbon for a time rangingin general from 1 to 4 hours.

According to another method, a porous carrier such as SiO₂ or Al₂ O₃having a low content of OH groups (preferably less than 1% by weight) isimpregnated with a liquid adduct Mg dihalide/alcohol; then the carrieris treated with an excess of TiCl₄ containing in solution theelectron-donor compound according to the procedure described, forexample, in German Patent Application No. 3,022,738 or in Belgian PatentNo. 868,682.

In all the above methods the final product contains a Mg dihalide in theactive form as defined hereinafter. By "active form of the Mg dihalide"is meant the Mg dihalides showing, in the X-raus powder spectrum ofcomponent (c), a broadening of at least 30% of the most intensediffraction line appearing in the powder spectrum of the correspondingdihalide having a surface area of 1 m² /g, or is meant the Mg dihalidesshowing an X-rays spectrum in which said most intense diffraction lineis replaced by a halo with its intensity peak shifted with respect tothe interplanar distance of the most intense line.

Very active forms of Mg dihalides are those showing an X-rays powderspectrum in which the most intense diffraction line appearing in thespectrum of the corresponding halide having a surface area of 1 m² /ghas a decreased intensity and is broadened to form a halo, or are thosein which said most intense line is replaced by a halo having itsintensity peak shifted with respect to the interplanar distance of themost intense line.

In general, the surface area of the above forms is higher than 30-40 m²/g and in particular is comprised between 100 and 300 m² /g.

Preferred Mg dihalides are MgCl₂ and MgBr₂. The water content of thedihalides in general is lower than 1% by weight.

Other known methods for preparing a Mg dihalide in active form orcatalyst components containing Ti and supported on a Mg dihalide, inwhich components the Mg dihalide is present in active form, are based onthe following reactions:

reaction of a Grignard compound or of a compound MgR₂ (R is hydrocarbyl)or of complexes MgR₂ /Al-trialkyls with halogenating agents, as AlX₃ orcompounds AlRmXn (X is halogen, R is hydrocarbyl, m+n=3), SiCl₄ orHSiCl₃ ;

reaction of a Grignard compound with a silanol or a polysiloxane, H₂ Oor with an alcohol and subsequent reaction with a halogenating agent orwith TiCl₄ ;

reaction of Mg with an alcohol and with a hydrogen halide, or of Mg witha hydrocarbyl halide and with an alcohol;

reaction of MgO with Cl₂ or AlCl₃ ;

reaction of MgX₂.nH₂ O (X is halogen) with a halogenating agent or withTiCl₄ ;

reaction of Mg mono- or dialcoholates or of Mg carboxylates with ahalogenating agent.

Suitable titanium halides and halogen-alcoholates are, in particular,the Ti tetrahalides, the Ti trihalides and the Titrihalogen-alcoholates. Preferred compounds are: TiCl₄, TiBr₄,2,6-dimethylphenoxytrichlorotitanium and trichlorophenoxy-titanium.

The Ti trihalides are obtained by known methods, for instance byreduction of TiCl₄ with Al or with a metalorganic compound of Al or withhydrogen.

In the case of the Ti trihalides it can be expedient to improve theperformance of the catalysts, to carry out an oxidation, even partial,of the titanium during or after the preparation of component (c). Tothis end, halogens and iodine halides can be employed.

Preferred catalysts are those in which component (c) is obtained fromMgCl₂, TiCl₄ or Cl₃ TiOC₆ H₅ and esters of maleic or malonic acid orfrom diisoamyl ether or benzophenone, and in which component (b) isphenyl- or ethyl-triethoxy-silane or diphenyl-dimethoxy-silane ordiphenyl-diethoxy-silane.

Component (a) is an Al-trialkyl, as Al-triethyl or Al-triisobutyl.

The preferred methods for the preparation of component (c) are thosedescribed in British Patent No. 1,559,194, Belgian Patent No. 868,682,published German Patent Applicaton No. 2,924,029, U.S. Pat. No.4,220,554, U.S. Pat. No. 4,328,122 or published German PatentApplication No. 3,022,738.

Among the preferred methods for preparing component (c) there is alsothe co-grinding of MgCl₂, TiCl₄ and electron-donor and the treatment ofthe ground product with a halogenated hydrocarbon, as1,2-dichloroethane.

The catalysts according to the invention are employed to polymerizealpha-olefins by known methods, that is by carrying out thepolymerization in liquid phase, either in the presence or in the absenceof an inert hydrocarbon solvent, or in gas phase or also by combining,for instance, a polymerization step in liquid phase with a step in gasphase.

In general, the temperature is comprised between 40° and 160° C., butpreferably between 60° and 90° C., operating either at atmosphericpressure or at higher pressure.

As a molecular weight regulator can be employed hydrogen or anotherregulator of known type.

The catalysts are particularly suitable for the polymerization ofpropylene, butene-1, styrene and 4-methyl-pentene-1. The catalysts canalso be employed for polymerizing, by known methods, mixtures ofpropylene and ethylene to produce modified polypropylene having improvedimpact resistance at low temperatures (the so-called propylene/ethyleneblock copolymers) or to obtain crystalline random copolymers ofpropylene with minor proportions of ethylene.

The test for the determination of the complexability of compound (b) iscarried out by using a potentiograph Metrohm model E 536 equipped withtitration bench E 535, automatic burette E 552, magnetic stirrer E 549and titration cell EA 880. A combined electrode EA 281 (Pt/Ag/AgCl/KCl3M) is employed.

As titrating agent is employed a 0.5M hexane solution of Al-triethylwhich is added to a 0.5M benzene solution of the compound underexamination. It is operated at room temperature under nitrogenatmosphere. The test of reactivity of the electron-donor compound withMgCl₂ is carried out under the following conditions:

Into a flask of 500 cc capacity are introduced, under nitrogenatmosphere, 2 g MgCl₂ (21 mMoles) suspended in 200 cc toluene and 3.5mMoles of the electron-donor under examination. It is allowed to reactat 25° C. for 1 hour and the solid is filtered and washed with 200 cctoluene and then with 200 cc n-heptane. The solid is isolated, dried andanalyzed.

As MgCl₂ is employed the product obtained from MgCl₂.2.5C₂ H₅ OH byreaction with Al-triethyl according to the following procedure: into a3000 cc flask are introduced 2340 cc of a 0.83M hexane solution of Al(C₂H₅)₃ ; while maintaining the temperature below 10° C., 136 g MgCl₂.2.5C₂H₅ OH are added little by little. After the addition is completed, it isheated at 70° C. for 4 hours; then the solid is filtered, washedrepeatedly with n-heptane and dried under a vacuum of 0.2-0.5 Torr.

The surface area of the obtained MgCl₂ amounts to 618 m² /g and thepores volume to 0.532 cc/g.

The following non-limiting examples are given to illustrate theinvention in even more detail.

EXAMPLES 1-16 AND COMPARATIVE EXAMPLES 1-4 Preparation of the SolidCatalyst Component

Into a vibrating mill having a total volume of 1 liter and containing 3kg steel balls of 16 mm diameter were introduced, under nitrogenatmosphere, 50 g anhydrous MgCl₂, an electron-donor compound in suchamount as to have a molar ratio MgCl₂ monofunctional electron-donorequal to 6 and a molar ratio MgCl₂ /bifunctional electron-donor equal to12, and TiCl₄ in the molar ratio 1/1 with respect to the electron-donorcompound. The whole was ground for 72 hours.

10 g of the co-ground product were treated with 100 cc1,2-dichloroethane for 2 hours at 80° C.; it was filtered at the sametemperature and after several washings with n-heptane the solid catalystcomponent was suspended in heptane.

Polymerization

Into a stainless steel autoclave of 3000 cc holding capacity, equippedwith magnetic anchor stirrer and thermometer, heat stabilized at 60° C.,and into which propylene was made to flow, was introduced a suspensionconsisting of 1000 cc anhydrous and deaerated n-heptane, 5 millimolesaluminum triethyl, the desired amount of the silicon compound and thesolid catalyst component.

Hydrogen was then introduced at a pressure of 0.2 atmospheres and themass was heated rapidly at 70° C. while simultaneously feeding inpropylene up to a total pressure of 7 atmospheres.

Solid pressure was kept constant over the whole polymerization time byfeeding in the monomer continuously. After 4 hours the polymerizationwas stopped and the polymer was isolated by filtration and dried. Thequantity of polymer dissolved in the filtrate was isolated, weighed andsummed to the polymer soluble in boiling n-heptane for the calculationof the isotacticity index (I.I.).

The results of the polymerization runs are reported in the Table.

In the Table are also reported the results of the tests ofextractability with Al-triethyl. The tests were carried out under thefollowing standard conditions:

Into a 5 liter flask are introduced 4 liters of anhydrous and deaeratedn-heptane containing 20 m Moles Al(C₂ H₅)₃. The temperature is raised to70° C., about 1 g of solid catalyst component is introduced and thewhole is allowed to react under stirring for 15 minutes. Thereupon it iscooled rapidly at 0° C. and is filtered, thus isolating a solid which isdried under vacuum at 25° C. and analyzed.

                                      TABLE                                       __________________________________________________________________________    SOLID CATALYST COMPONENT                                                      Electron-donor (ED)     Extraction with Al(C.sub.2 H.sub.5).sub.3             Example          % by weight                                                                          % by weight                                                                           Surface area                                  No.  Type        (1)    (3)     (M.sup.2 /g)                                  __________________________________________________________________________    1    Di-n-butyl maleate                                                                        6.2    0       186                                           2    Di-n-butyl itaconate                                                     3    Diethyl allylmalonate                                                    4    Di-n-butyl malonate                                                      5    Diisobutyl succinate                                                     6    Di-n-butyl succinate                                                     7    Benzophenone                                                             8    Ethyl trichloroacetate                                                                    9.2    0.54    186                                           9    Ethyl benzoate                                                                            8.8    0.8     163                                           10   Diisoamyl ether (2)                                                                       1      0       163                                           11   α-Methyl-α-phenyl-                                                            7.3    0.9      90                                                γ-butyrolacetone                                                   12   POCl.sub.3                                                               13   Triphenylphosphine                                                       14   Ethyl acetate                                                                             4.2    0       229                                           15                                                                                  ##STR2##   9.4    0.3     174                                           16   Diisobutyl o.phenylene                                                                    6.7    0.9     165                                                diacetate                                                                1    2-Ethylhexyl terephta-                                                                    9.2    0.26     1                                            compar.                                                                            late                                                                     2    Phenothiazine                                                                             7.7    3.6                                                   compar.                                                                       3    Diisobutyl O,Odiphe-                                                                      6.6    2.4                                                   compar.                                                                            nyldicarboxylate                                                         4    Isobutyl m-acetoxy-                                                                       8.8    4.2                                                   compar.                                                                            benzoate                                                                 __________________________________________________________________________    POLYMERIZATION                                                                                       Yield g                                                                  Al/Si                                                                              PP/g                                                   Example                                                                             Silicon     molar                                                                              catalyst                                                                             I.I.                                                                              η  inh                                  No.   compound    ratio                                                                              component                                                                            (%) (dl/g)                                      __________________________________________________________________________    1     (C.sub.6 H.sub.5).sub.2 Si(OCH.sub.3).sub.2                                               10   8600   95.1                                                                              1.5                                         2     (C.sub.6 H.sub.5).sub.2 Si(OCH.sub.3).sub.2                                               10   4600   93.6                                                                              1.4                                         3     (C.sub.6 H.sub.5).sub.2 Si(OCH.sub.3).sub.2                                               10   8500   97.3                                                                              1.6                                         4     (C.sub.6 H.sub.5).sub.2 Si(OCH.sub.3).sub.2                                               10   5000   91.2                                                                              1.3                                         5     (C.sub.6 H.sub.5).sub.2 Si(OCH.sub.3).sub.2                                               10   4000   90  1.2                                         6     (C.sub.6 H.sub.5).sub.2 Si(OCH.sub.3).sub.2                                               10   3600   91.5                                                                              1.3                                         7     (C.sub.6 H.sub.5).sub.2 Si(OCH.sub.3).sub.2                                               3.3  3600   93.8                                                                              1.2                                         8     (C.sub.6 H.sub.5)Si(OC.sub.2 H.sub.5).sub.3                                               3.3  5600   92.2                                                                              1.1                                         9     (C.sub.6 H.sub.5)Si(OC.sub.2 H.sub.5).sub.3                                               10   4500   95.5                                                                              1.1                                         10    (C.sub.6 H.sub.5)Si(OC.sub.2 H.sub.5).sub.3                                               5    5200   91  1.3                                         11    (C.sub.6 H.sub.5)Si(OC.sub.2 H.sub.5).sub.3                                               5    3600   91.8                                                                              1.2                                         12    (C.sub.6 H.sub.5)Si(OC.sub.2 H.sub.5).sub.3                                               5    4000   92  1.5                                         13    (C.sub.6 H.sub.5)Si(OC.sub.2 H.sub.5 ).sub.3                                              5    3600   90.5                                                                              1.2                                         14    (C.sub.6 H.sub.5)Si(OC.sub.2 H.sub.5).sub.3                                               10   3200   96.6                                                                              1.2                                         15    (C.sub.6 H.sub.5)Si(OC.sub.2 H.sub.5).sub.3                                               20   5500   91.3                                                                              1.5                                         16    (C.sub.6 H.sub.5)Si(OC.sub.2 H.sub.5).sub.3                                               20   3500   90.7                                                                              1.2                                         1     (C.sub.6 H.sub.5)Si(OC.sub.2 H.sub.5).sub.3                                               10   2300   88  1.1                                         compar.                                                                       2     (C.sub.6 H.sub.5)Si(OC.sub.2 H.sub.5).sub.3                                               10   1300   71.8                                                                              1.2                                         compar.                                                                       3     (C.sub.6 H.sub.5)Si(OC.sub.2 H.sub.5).sub.3                                               10   trace  --  --                                          compar.                                                                       4     (C.sub.6 H.sub.5)Si(OC.sub.2 H.sub.5).sub.3                                               10   550    84.4                                                                              1.2                                         compar.                                                                       __________________________________________________________________________     (1) The percent amount of ED is referred to the solid after washing with      1,2dichloroethane.                                                            (2) The diisoamyl ether content of the ground product, before washing wit     1,2dichloroethane, was 17%.                                                   (3) The percent of ED remaining on the solid of the extraction with           Al(C.sub.2 H.sub.5).sub.3.                                               

We claim:
 1. A solid component to be employed, in combination withmetallorganic Al compounds and with electron-donor compounds which arenot completely complexed with Al-triethyl at the equivalent point of apotentiometric titration under standard conditions but reactive towardanhydrous Mg chloride, to form catalysts for the polymerization ofalpha-olefins CH₂ =CHR, said component comprising a titanium compoundhaving at least a Ti-halogen bond and an electron-donor compound bothsupported on an anhydrous Mg dihalide, the electron-donor compound beingselected from the group consisting of diisoamyl ether, triphenylphosphite, α-methyl-α-phenyl-γ-butyrolactone and the following classesof esters:(1) di-n-butyl succinate and di-isobutyl succinate; (2) estersof unsaturated polycarboxylic acids in which two carboxyl groups arelinked to vicinal, double bond-forming carbon atoms and in which thehydrocarbyl radical or radicals of the COOR groups are linear saturatedor unsaturated radicals or cycloaliphatic radicals with 2-20 carbonatoms or hydrocarbyl esters of unsaturated linear or branchedpolycarboxylic acids with 1-20 carbon atoms in which the carboxy groupsare not linked to vicinal double bond-forming carbon atoms; (3)hydrocarbyl esters of aromatic meta- and paradicarboxylic acids andhydrocarbyl esters of polycarboxylic aromatic acids containing more thantwo carboxyl groups; (4) hydrocarbyl esters of aromatic hydroxycompounds containing the OH groups in meta- or para-position and estersof aromatic hydroxy acids the OH groups of which are in meta- orpara-position with respect to the carboxyl group; (5) hydrocarbyl estersof polycarboxylic acids in which at least one carboxyl group is linkedto an aromatic ring and at least one other is linked to carbon atom ofan aliphatic chain or to a cycloaliphatic ring or at least two carbonylgroups are linked to an aromatic ring through an alkylene group; (6)esters of aromatic polycarboxylic acids containing at least twonon-condensed aromatic rings, each bearing a carboxyl group; (7) estersof carbonic acid with glycols, and carbonic acid derivatives of formulaRO--CO--OR' wherein R and R' are the same or different acyl groups with1-20 carbon atoms; (8) esters of polyols and of monohydroxy-phenols; and(9) hydrocarbyl esters of acetylenic acids; the electron-donor compoundsbeing extractable from the solid for at least 70% by mols withAl-triethyl under standard measurement conditions, and the surface areaof the solid subjected to extraction being higher than 20 m² /g.
 2. Asolid component according to claim 1, in which the Mg halide is MgCl₂.3. A solid component according to claim 1, in which the Mg halide isMgBr₂.